Journal of Visualization - Volume 11, issue 4

Article Type: Other

Citation: Journal of Visualization, vol. 11, no. 4, pp. 274-274, 2008

Authors: Dhananjaya Rao, G. | Swaminathan, S. | Rathakrishnan, E.

Article Type: Research Article

Citation: Journal of Visualization, vol. 11, no. 4, pp. 275-275, 2008

Authors: Yamagishi, Y. | Oki, M.

Article Type: Research Article

Citation: Journal of Visualization, vol. 11, no. 4, pp. 276-276, 2008

Authors: Imamura, O. | Watanuki, T. | Suzuki, K.

Article Type: Research Article

Citation: Journal of Visualization, vol. 11, no. 4, pp. 278-278, 2008

Authors: Polidori, G. | Beaumont, F. | Jeandet, P. | Liger-Belair, G.

Article Type: Research Article

Citation: Journal of Visualization, vol. 11, no. 4, pp. 279-279, 2008

Authors: Imamura, O. | Watanuki, T. | Suzuki, K. | Rathakrishnan, E.

Article Type: Research Article

Citation: Journal of Visualization, vol. 11, no. 4, pp. 280-280, 2008

Authors: Fujisawa, N. | Oguma, Y.

Article Type: Research Article

Citation: Journal of Visualization, vol. 11, no. 4, pp. 281-282, 2008

Authors: Osao, A. | Takakura, Y. | Arai, N.

Article Type: Research Article

Citation: Journal of Visualization, vol. 11, no. 4, pp. 283-284, 2008

Authors: Tardu, S. | Doche, O.

Article Type: Research Article

Abstract: The effect of blowing through a localized slot on the wall turbulence dynamics and heat transfer process is analyzed by direct numerical simulations in a fully developed turbulent channel flow. The severity parameter is mild and there is no flow separation induced by the blowing. The shear stress transport and temperature energy budget is discussed in detail. The wall shear and flux decreases immediately downstream the slot in a similar manner but the Reynolds analogy does …not hold over the slot. The physical process is governed by the production and pressure redistribution over the slot in a complex manner. The turbulent transport and especially the advection play an essential role in the heat transfer mechanism. Show more

Keywords: Localized blowing, Control of Wall turbulence, Direct Numerical Simulations, Heat transfer

Citation: Journal of Visualization, vol. 11, no. 4, pp. 285-298, 2008

Authors: Huang, X. | Wang, X. | Liao, G.

Article Type: Research Article

Abstract: Effervescent atomization is one of the twin-fluid atomization methods while it has better performance in terms of smaller drop sizes and/or lower injection pressures. In order to investigate the effects of the internal flow patterns on droplet characteristics, a new kind of effervescent atomizer was designed and manufactured. The bubble forming process was visualized with a high-speed camera, while the droplet size was characterized with a LDV/PDA system. The experimental results show that there are three …regimes of the two-phase flows inside the discharge orifice, one is bubbly flow, another is annular flow while the other is the intermittent flow. The flow patterns transfered from bubbly flow to intermittent flow and then to annular flow with decreasing of the water flow rate. In addition, with increasing of the working pressure or decreasing of the water flow rate, the SMD (Sauter mean diameter) of the droplets decreased and the axial mean velocity increased. Show more

Keywords: Visualization, Water mist, Effervescent atomization, Two phase flow

Citation: Journal of Visualization, vol. 11, no. 4, pp. 299-308, 2008

Authors: Nastase, I. | Meslem, A.

Article Type: Research Article

Abstract: Classical planar 2D-PIV measurements and time-resolved visualizations enriched by low-level processing are used for the reconstruction of the Kelvin-Helmholtz vortex passing in the near field of a circular and a 6-lobed orifice jet flow. In the circular jet, the entrainment is produced in the braid region, being interrupted in the presence of the Kelvin-Helmholtz ring. The latter compresses the streamwise vortices and alters their self-induction role. Conversely, the 6-lobed orifice geometry allows the …cutting of the Kelvin-Helmholtz structures into discontinuous ring segments. Consequently, into these discontinuity regions streamwise large scale structures are developing. These streamwise structures are permanent thus controlling and enhancing the jet entrainment which is not altered by the Kelvin-Helmholtz structures passing. Show more

Keywords: Jet flow, Kelvin-Helmholtz vortex, Streamwise vortex, Image processing

Citation: Journal of Visualization, vol. 11, no. 4, pp. 309-318, 2008

Authors: Maidi, M. | Yao, Y.

Article Type: Research Article

Abstract: Direct numerical simulations have been performed in this study to visualize the flow behavior of single and multiple square jets issuing normally into a cross-flow. Three configurations are considered, a single jet located in the centre of the domain, twin jets in side-by-side (SBS) arrangement in the spanwise direction and triple jets in tandem arrangement with twin jets at the front and a third jet in downstream along the centre line. Simulation uses a jet to …cross-flow velocity ratio of 2.5 and the Reynolds number 225, based on the free-stream quantities and the jet width. While the vortical structures predicted from single jet case were in good qualitatively agreement with the findings of other researchers, our results show that the process of merging between two counter-rotating vortex pairs (CRVP) in twin jets configurations is strongly dependent on the jet-to-jet edge distance. Further downstream in the far-field, results from the SBS twin jets show a most dominating larger CRVP accompanied with a smaller inner vortex pair. The observations are in good qualitative agreement with the experimental findings in the literature. The resulting flow structures of triple jets in tandem configuration have revealed, for the first time, more complicated flow interactions between individual jets and cross-flow, providing further insights of complex flow physics and its potential engineering applications. Show more

Keywords: Direct numerical simulation, Jets in cross-flow, Vortex flow structure and interaction

Citation: Journal of Visualization, vol. 11, no. 4, pp. 319-327, 2008

Authors: Li, C. | Xu, C. N. | Zhang, L. | Yamada, H. | Imai, Y.

Article Type: Research Article

Abstract: We have successfully demonstrated that the stress distribution of a metal material can be directly displayed by coating the surface of test objects with an upgraded strong mechanoluminescence (ML) material of SrAl2O4:Eu (SAO). In this paper an aluminum plate with the SAO sensing film was applied to experimental analysis of stress concentrations. And the comparison with a numerical analysis showed that the ML intensity of SAO sensing film correlates linearly with stress on metal surface and …the observed real-time ML images quantitatively reflect stress concentration. This novel visualisation technique can be applied to view stress concentration in various fields such as modelling, manufacturing and demonstration of industrial products as well as to point out danger areas in structural objects such as pipelines and bridges. Show more

Keywords: Visualization, Mechanoluminescence, Stress distribution

Citation: Journal of Visualization, vol. 11, no. 4, pp. 329-335, 2008

Authors: Sohn, M. H. | Lee, K. Y. | Chang, J. W.

Article Type: Research Article

Abstract: An off-surface visualization method using micro water droplets and a laser beam sheet was developed. The average size of the water droplets generated by the home-style ultrasonic humidifier was about 5-10 μm. This method was pollution-free, eliminated the problem of toxicity, and provided a sufficient density of tracing particles for good visibility. The method was successfully applied to a visualization of the complex vortex flow of a double-delta wing with strake.

Keywords: Micro Water Droplets, Off-surface Visualization, Delta-wing, Vortex Flow

Citation: Journal of Visualization, vol. 11, no. 4, pp. 337-346, 2008

Authors: Sznitman, J. | Rösgen, T.

Article Type: Research Article

Abstract: Flow visualizations are presented for acoustic streaming occurring inside spherical elastic cavities oscillating in an acoustic field. Streaming flows are visualized using Particle Image Velocimetry (PIV) and results are observed for a range of values of a dimensionless frequency parameter, M = 120-306. Over the frequency range investigated, streaming flow fields remain steady at a given value of M. The magnitude of the flows circulating inside the cavity remains small (< 1 mm/s) and follows a …non-linear dependency with respect to the acoustic power of the sound wave. The present boundary-driven cavity flows may enhance particle fluid transport mechanisms, leading ultimately to potential fluid mixing applications. Show more

Keywords: Acoustic streaming, Cavity flow, Low Reynolds number flow, PIV

Citation: Journal of Visualization, vol. 11, no. 4, pp. 347-355, 2008

Authors: Youn, C. | Asano, S. | Kawashima, K. | Kagawa, T.

Article Type: Research Article

Abstract: Pressure reducing valves are widely used to maintain the pressure of gas reservoirs to specific values. In a normal valve, supply pressure is decompressed with an orifice structure. When compressed air passes through the orifice structure, considerable noise occurs at the downstream side. In this paper, we have developed a radial slit structure that can reduce pressure without noise. The noise is reduced by changing the orifice structure into the radial slit structure. The radial slit …structure valve reduces pressure without noise by suppressing the generation of turbulence and shock wave at the downstream. The analysis of the flow in radial slit structure was achieved by CFD2000 software. The flow rate and pressure distribution were simulated and compared with the experimental result. To confirm the generation of shock wave, the flow of orifice and radial slit structure at the downstream was visualized by Schlieren photography method. A shock wave was generated in the orifice structure, but no shock wave was generated in the radial slit structure. Noise reduction efficiency was investigated by the experiment. The experiment apparatus was set up to JIS standards. The experimental results indicated that the noise level decreased by approximately 40 dB in the slit structure. It is confirmed that the radial slit structure has effectiveness for low noise in the pressure reducing flow. And, it is expected that it can be applied to various kinds of industrial fields. Show more

Keywords: Pneumatics, Radial Slit Structure valve, Schlieren, Shock Wave, Noise

Citation: Journal of Visualization, vol. 11, no. 4, pp. 357-364, 2008

Authors: Nashimoto, A. | Fujisawa, N. | Nakano, T. | Yoda, T.

Article Type: Research Article

Abstract: The purpose of this study is to understand the aerodynamic noise source distribution around a rotating fan blade by measuring the noise signal and velocity field around the blade. The local noise-level distribution over the fan blade is measured by microphone arrays, and the flow field is visualized by smoke and phase-averaged PIV measurement. The noise source distribution is examined by cross-correlation analysis between noise signal and velocity fluctuation. It is found that the noise source …is located near the rotating fan blade, especially around leading and trailing edges. The separation and reattachment of flow are observed near the leading edge, and the tip vortices and vortex shedding are found near the trailing edge. The cross-correlation distribution of the noise signal and the radial velocity fluctuation shows large magnitude in the correlated regions, which indicates the noise generation by the formation of vortex structure around the blade. Show more

Keywords: Aerodynamic noise, Noise source, Flow visualization, PIV, Fan, Measurement

Citation: Journal of Visualization, vol. 11, no. 4, pp. 365-373, 2008

Authors: Machida, M. | Kaminoyama, M.

Article Type: Research Article

Abstract: Electrodynamic sensor, which can also be called as tribo-electric sensor, senses the electrostatic charge carried by the particle. The tomography system using electrodynamic sensor is called as tribo-electric tomography system. Source of the signal induced on the electrodynamic sensor is brought by the object to be measured and no excitation circuit is necessary. This electrodynamic sensing is a passive sensing and the fast and light weighted tomography system is expected. On the other hand, most of …tomography system, like capacitance tomography or resistance tomography, demands excitation circuit and is an active sensing. The number of measurements with the passive sensing is equal to the number of sensors and that of active sensing is the number of the combinations of two sensors. The passive sensing tomography system demands more sensors to be settled. We plan to improve in reconstructed images by increasing the number of the electrodynamic sensors in tribo-electric tomography system. We investigate the influence of surface area to signal intensity solving the electrical field in the sensing zone using finite element method. Show more

Keywords: Electrodynamic Sensor, Process Tomography, Finite Element Method, Electric Field

Citation: Journal of Visualization, vol. 11, no. 4, pp. 375-385, 2008

Authors: Fujisawa, N. | Brown, K. | Nakayama, Y. | Hyatt, J. | Corby, T.

Article Type: Research Article

Abstract: In this paper, implementation and visualization of scientific arts are described using some examples of application in subject research areas, such as sculpture, archeology, fine arts and information aesthetics, which have been discussed through the Scientific Art Session at FLUCOME9, Tallahassee, Florida, 2007-9. In the application to sculpture, stereo visualization techniques, such as anaglyph stereo visualization and integral imaging technique, are introduced to realize the three-dimensional geometry of sculpture to enhance visual …impact on the art. The second application is the flow visualization technique for archeology, where the vortices behind the river stones are studied to understand the origin of patterns on Jomon pottery. Interestingly, such vortex patterns also appear in the paintings of fine arts. The third example is the visualization of information aesthetics, where the Web information, such as public media and stock market, are visualized through scientific techniques. These examples of visualization of scientific arts provide the present state of the art in interdisciplinary visualization. Show more

Keywords: Visualization, Scientific arts, Sculpture, Archeology, Fine arts, Information aesthetics

Citation: Journal of Visualization, vol. 11, no. 4, pp. 387-394, 2008

Authors: Prenel, J. P.

Article Type: Research Article

Abstract: The 13th international Symposium on Flow Visualization (ISFV 13) was held in Nice, Acropolis Convention Center, France, July 1-4, 2008. In order to avoid duplication, the 12th French Congress on Visualization in Fluid Mechanics (Fluvisu 12) took place simultaneously. The symposium attracted 298 participants from 27 countries and was organized in 40 ORAL sessions, four invited lectures and a poster exhibition. The Asanuma and Leonardo da Vinci Awards were attributed to scientists for their outstanding contributions …to the field of flow visualization. A technical exhibition was organized in order to present recent optical systems and components. A video / photo contest allowed to reward the most aesthetic pictures presented during the symposium. Show more

Keywords: Flow Visualization, Imagery, Optical measurements, Velocimetry, Image Processing

Citation: Journal of Visualization, vol. 11, no. 4, pp. 395-400, 2008

Article Type: Other

Citation: Journal of Visualization, vol. 11, no. 4, pp. 401-405, 2008